1. Field of the Invention
This invention relates to information storage disk holding members made of glass-ceramics and an information storage disk drive device using the disk holding members. In this specification, xe2x80x9cholding membersxe2x80x9d mean members for holding an information storage disk in position in an information storage disk drive device and include, for example, a rotor hub in the form of a rotating column for holding one or more information storage disk, a disk supporting plane forming member on which information storage disks are stacked with a predetermined interval, a spacer ring and a shim, and a clamp as a mounting member.
An information storage disk drive device is generally constructed in such a manner that one or more information storage disks and spacer rings are mounted alternately on a rotor hub which is secured fixedly to a rotor shaft and these disks and spacer rings are finally clamped with a shim and a clamp. The holding members such as the rotor hub and spacer rings are normally made of metal materials such as stainless steel and an aluminum alloy. There is, however, an increasing tendency toward using a disk substrate made of glass-ceramics in lieu of the conventional aluminum disk. In this case, use of a metal material for holding members is undesirable because there is a great difference in the coefficient of thermal expansion between the holding members and the substrate and, moreover, there occur distortion, deformation and flash in the course of processing of the holding members. Furthermore, since an aluminum alloy is a soft material, deformation tends to occur during a high speed rotation and, therefore, it cannot cope sufficiently with current requirement for a high density recording.
In this technical field, since a high precision is required for positioning of a head and a medium, a particularly high precision in size is required for component parts of a medium substrate and a disk. For this reason, it is desirable for information storage disk holding members to have as little difference as possible between other component parts of a disk drive device (hereinafter referred to xe2x80x9cother drive component partsxe2x80x9d) in the coefficient of thermal expansion within a temperature range of an environment in which the drive device is used. It is also desirable for them to have a low dust producing property, a high reliability, a low cost and a good polishing property. There is demand for a more suitable material for information storage disk holding members which satisfies all of these requirements.
As materials for solving these problems, there have been proposed polycrystalline ceramics (Japanese Patent Application Laid-open Publication No. Sho 61-148667 and Japanese Patent Application Laid-open Publication No. Hei 9-44969 etc.) and amorphous glass (Japanese Patent Application Laid-open Publication No. Hei 10-74350 etc.) but satisfactory solution has not been achieved yet.
It is an object of the present invention to provide information storage disk holding members which have solved the above described problems and are capable of coping with a high speed rotation of a disk in conformity with tendencies toward high density recording and high speed transmission of information, increasing mechanical strength for adaptation to mobile uses, having a thermal expansion property matching that of other drive component parts and eliminating defects caused by dissolving out of alkali, and also to provide an information storage disk drive device using these holding members.
As a result of studies and experiments made by the inventors of the present invention for achieving the above described object of the invention, it has been found, which has led to the present invention, that, by heat treating a base glass of a proper composition such as a SiO2xe2x80x94Li2Oxe2x80x94K2Oxe2x80x94P2O5xe2x80x94Al2O3xe2x80x94ZrO2 glass under proper conditions, glass-ceramics having a high Young""s modulus, a low specific gravity, a coefficient of thermal expansion, a high mechanical strength and a low dust producing property and being thereby capable of coping with a high speed rotation of a disk and very suitable for information storage disk holding members, particularly for spacer rings, can be obtained.
As the first aspect of the invention, the invention described in claim 1 is an information storage disk holding member for holding an information storage disk in position, said holding member being made of glass-ceramics in which a crystal phase is dispersed in a glass matrix.
The invention described in claim 2 is an information storage disk holding member as defined in claim 1 wherein specific rigidity (Young""s modulus/specific gravity) is not smaller than 37 GPa and specific gravity is not greater than 3.0.
The invention described in claim 3 is an information storage disk holding member as defined in claim 1 wherein Young""s modulus is within a range from 95 GPa to 130 GPa and specific gravity is within a range from 2.40 to 2.60.
The invention described in claim 4 is an information storage disk holding member as defined in claim 1 wherein bending strength is within a range from 400 MPa to 800 MPa.
The invention described in claim 5 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of lithium disilicate (Li2Oxe2x96xa12SiO2), xcex1-quartz (xcex1-SiO2), xcex1-quartz solid solution (xcex1-SiO2 solid solution), xcex1-cristobalite (xcex1-SiO2) and xcex1-cristobalite solid solution (xcex1-SiO2 solid solution).
The invention described in claim 6 is an information storage disk holding member as defined in claim 5 wherein the glass-ceramics comprise, as a predominant crystal phase, lithium disilicate.
The invention described in claim 7 is an information storage disk holding member as defined in claim 1 wherein an amount of crystal of lithium disilicate in the glass-ceramics is 3-10 mass % and an average crystal grain diameter of the crystal phase is within a range from 0.01 xcexcm-0.05 xcexcm.
The invention described in claim 8 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 9 is an information storage disk holding member as defined in any of claims 1-8 wherein coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +70xc2x0 C. is within a range from +65xc3x9710xe2x88x927/xc2x0 C. to +130xc3x9710xe2x88x927/xc2x0 C.
As the second aspect of the invention, the invention described in claim 10 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprises, as a predominant crystal phase, xcex1-quartz (xcex1-SiO2) or xcex1-quartz solid solution (xcex1-SiO2 solid solution), an amount of the crystal phase is 3-35 mass %, and an average crystal grain diameter of the crystal phase is not greater than 0.10 xcexcm.
The invention described in claim 11 is an information storage disk holding member as defined in claim 10 wherein an average crystal grain diameter of the entire predominant crystal phase of the glass-ceramics is not greater than 0.05 xcexcm.
The invention described in claim 12 is an information storage disk holding member as defined in claim 10 wherein the glass-ceramics are substantially free of PbO.
The invention described in claim 13 is an information storage disk holding member as defined in claim 10 wherein coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +70xc2x0 C. is within a range from +95xc3x9710xe2x88x927/xc2x0 C. to +110xc3x9710xe2x88x927/xc2x0 C.
The invention described in claim 14 is an information storage disk holding member as defined in claim 10 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 15 is an information storage disk holding member as defined in any of claims 10-14 wherein an amount of crystal of lithium disilicate in the glass-ceramics is within a range from 15 mass % to 40 mass %.
As the third aspect of the invention, the invention described in claim 16 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of cordierite (Mg2Al4Si5O18), cordierite solid solution (Mg2Al4Si5O18 solid solution), spinel, spinel solid solution, enstatite (MgSiO3), enstatite solid solution (MgSiO3 solid solution), xcex2-quartz (xcex2-SiO2), xcex2-quartz solid solution (xcex2-SiO2 solid solution), magnesium titanate (MgTi2O5) and magnesium titanate solid solution (MgTi2O5 solid solution).
The invention described in claim 17 is an information storage disk holding member as defined in claim 16 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 18 is an information storage disk holding member as defined in claim 16 or 17 wherein coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +70xc2x0 C. is within a range from +30xc3x9710xe2x88x927/xc2x0 C. to +65xc3x9710xe2x88x927/xc2x0 C.
As the fourth aspect of the invention, the invention described in claim 19 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of enstatite (MgSiO3), enstatite solid solution (MgSiO3 solid solution), magnesium titanate (MgTi2O5), magnesium titanate solid solution (MgTi2O5 solid solution), spinel and spinel solid solution, the glass-ceramics comprise Al2O3 in an amount of less than 20 mass %, and the glass-ceramics have Young""s modulus within a range from 115 GPa to 160 GPa.
The invention described in claim 20 is an information storage disk holding member as defined in claim 19 wherein the glass-ceramics comprise enstatite (MgSiO3) or enstatite solid solution (MgSiO3 solid solution) as a crystal phase having the largest precipitation amount (first phase).
The invention described in claim 21 is an information storage disk holding member as defined in claim 19 wherein the glass ceramics comprise magnesium titanate (MgTi2O5) or magnesium titanate solid solution (MgTi2O5 solid solution) as a crystal phase having the largest precipitation amount (first phase).
The invention described in claim 22 is an information storage disk holding member as defined in claim 20 wherein the glass-ceramics comprise, as a crystal phase having a precipitation amount which is smaller than the precipitation amount of the first phase, at least one crytal phase selected from the group consisting of magnesium titanate (MgTi2O5), magnesium titanate solid solution (MgTi2O5 solid solution), spinel and spinel solid solution.
The invention described in claim 23 is an information storage disk holding member as defined in claim 21 wherein the glass-ceramics comprise, as a crystal phase having a precipitation amount which is smaller than the precipitation amount of the first phase, at least one crytal phase selected from the group consisting of enstatite (MgSiO3), enstatite solid solution (MgSiO3 solid solution), spinel and spinel solid solution.
The invention described in claim 24 is an information storage disk holding member as defined in claim 19 wherein the glass-ceramics are substantially free of Li2O, Na2O and K2O.
The invention described in claim 25 is an information storage disk holding member as defined in claim 19 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 26 is an information storage disk holding member as defined in claim 19 wherein the glass-ceramics comprise an element selected from P, W, Nb, La, Y and Pb in an amount of up to 3 mass % on oxide basis and/or an element selected from Cu, Co, Fe, Mn, Cr, Sn and V in an amount of up to 2 mass % on oxide basis.
The invention described in claim 27 is an information storage disk holding member as defined in claim 19 wherein coefficient of thermal expansion within a range from xe2x88x92b 50xc2x0 C. to +70xc2x0 C. is within a range from +40xc3x9710xe2x88x927/xc2x0 C. to +60xc3x9710xe2x88x927/xc2x0 C.
The invention described in claim 28 is an information storage disk holding member as defined in claim 19 wherein a crystal grain diameter of the respective crystal phases is within a range from 0.05 xcexcm 0.30 xcexcm.
The invention described in claim 29 is an information storage disk holding member as defined in any of claims 19-28 wherein Vickers"" hardness is within a range from 700 to 850.
As the fifth aspect of the invention, the invention described in claim 30 is an information storage disk holding member as defined in claim 1 wherein a predominant crystal phase or phases of the glass-ceramics are at least one crystal phase selected from the group consisting of xcex2-quartz, xcex2-quartz solid solution, enstatite, enstatite solid solution, forsterite and forsterite solid solution.
The invention described in claim 31 is an information storage disk holding member as defined in claim 30 wherein the glass-ceramics comprise Al2O3 in an amount within a range from 10 mass % to less than 20 mass % on oxide basis and have Young""s modulus (GPa)/specific gravity within a range from 37 to 63.
The invention described in claim 32 is an information storage disk holding member as defined in claim 30 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 33 is an information storage disk holding member as defined in claim 30 wherein the glass-ceramics are substantially free of Na2O, K2O and PbO.
The invention described in claim 34 is an information storage disk holding member as defined in any of claims 30-33 wherein a crystal grain diameter of the respective crystal phases is within a range from 0.05 xcexcm to 0.30 xcexcm.
As the sixth aspect of the invention, the invention described in claim 35 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of cordierite, cordierite solid solution, spinel, spinel solid solution, enstatite, enstatite solid solution, xcex2-quartz and xcex2-quartz solid solution.
The invention described in claim 36 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of xcex2-quartz, xcex2-quartz solid solution, enstatite, enstatite solid solution, forsterite and forsterite solid solution.
The invention described in claim 37 is an information storage disk holding member as defined in claim 35 wherein a crystal grain diameter of the respective crystal phases is within a range from 0.05 xcexcm to 0.30 xcexcm.
The invention described in claim 38 is an information storage disk holding member as defined in claim 35 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 39 is an information storage disk holding member as defined in claim 35 wherein the glass-ceramics have Young""s modulus (GPa)/specific gravity within a range from 37 to 63 and comprise Al2O3 within a range from 10% to less than 20%.
The invention described in claim 40 is an information storage disk holding member as defined in claim 35 wherein the glass-ceramics are substantially free of Na2O, K2O and PbO.
The invention described in claim 41 is an information storage disk holding member as defined in any of claims 35-40 wherein coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +70xc2x0 C. is within a range from +30xc3x9710xe2x88x927/xc2x0 C. to +50xc3x9710xe2x88x927/xc2x0 C.
As the seventh aspect of the invention, the invention described in claim 42 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of xcex2-quartz (xcex2-SiO2), xcex2-quartz solid solution (xcex2-SiO2 solid solution), xcex2-spodumene (xcex2-Li2O.Al2O3.SiO2), xcex2-spodumene solid solution (xcex2-Li2O.Al2O3.SiO2 solid solution), xcex2-eucryptite (xcex2-Li2O.Al2O3.2SiO2 where a part of Li2O is replaceable by MgO and/or ZnO) and xcex2-eucryptite solid solution (xcex2-Li2O.Al2O3.2SiO2 solid solution where a part of Li2O is replaceable by MgO and/or ZnO).
The invention described in claim 43 is an information storage disk holding member as defined in claim 42 wherein an average crystal grain diameter of the glass-ceramics is within a range from 0.001 xcexcm to 0.10 xcexcm.
The invention described in claim 44 is an information storage disk holding member as defined in claim 42 wherein the glass-ceramics comprise, in mass % on oxide basis,
and are substantially free of PbO, Na2O and K2O.
The invention described in claim 45 is an information storage disk holding member as defined in any of claims 42-44 wherein coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +600xc2x0 C. is within a range from xe2x88x9210xc3x9710xe2x88x927/xc2x0 C. to +20xc3x9710xe2x88x927/xc2x0 C.
As the eighth aspect of the invention, the invention described in claim 46 is an information storage disk holding member as defined in claim 1 wherein a predominant crystal phase of the glass-ceramics is gahnite (ZnAl2O3) and/or gahnite solid solution (ZnAl2O3 solid solution).
The invention described in claim 47 is an information storage disk holding member as defined in claim 46 wherein the glass-ceramics are substantially free of PbO, Na2O and K2O.
The invention described in claim 48 is an information storage disk holding member as defined in claim 46 wherein the glass-ceramics comprise, in mass % on oxide basis,
The invention described in claim 49 is an information storage disk holding member as defined in any of claims 46-48 wherein coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +600xc2x0 C. is within a range from xe2x88x9235xc3x9710xe2x88x927/xc2x0 C. to +65xc3x9710xe2x88x927/xc2x0 C.
As the ninth aspect of the invention, the invention described in claim 50 is an information storage disk holding member as defined in claim 1 wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of xcex1-cristobalite, xcex1-cristobalite solid solution, xcex1-quartz and xcex1-quartz solid solution but are substantially free of lithium disilicate (Li2O.2SiO2), lithium silicate (Li2O.SiO2), xcex2-spodumene, xcex2-eucryptite, xcex2-quartz, mica and fluorrichterite and also are free of Cr and Mn, have a coefficient of thermal expansion within a range from xe2x88x9250xc2x0 C. to +70xc2x0 C. which is within a range from +65xc3x9710xe2x88x927/xc2x0 C. to +140xc3x9710xe2x88x927/xc2x0 C. and have an average crystal grain diameter of the predominant crystal phase of less than 0.10 xcexcm.
The invention described in claim 51 is an information storage disk holding member as defined in claim 50 wherein the glass-ceramics have Young""s modulus which is not smaller than 80 GPa.
The invention described in claim 52 is an information storage disk holding member as defined in claim 50 wherein the glass-ceramics have specific gravity within a range from 2.3 to 2.7.
The invention described in claim 53 is an information storage disk holding member as defined in claim 50 wherein the glass-ceramics have light transmittance for a plate thickness of 10 mm which is 90% or over within a wavelength range from 950 nm to 1600 nm.
The invention described in claim 54 is an information storage disk holding member as defined in claim 50 wherein the glass-ceramics have bending strength of 250 MPa or over.
The invention described in claim 55 is an information storage disk holding member as defined in claim 50 wherein the glass-ceramics have Vickers"" hardness within a range from 600 to 800.
The invention described in claim 56 is an information storage disk holding member as defined in any of claims 50-55 wherein the glass-ceramics comprise, in mass % on oxide basis,
As other aspect of the invention, the invention described in claim 57 is an information storage disk holding member as defined in any of claims 1, 10 and 16 wherein the glass-ceramics are obtained by subjecting base glass obtained by melting and forming glass raw materials to heat treatment for nucleation under a temperature within a range from 400xc2x0 C. to 600xc2x0 C. for one to seven hours and further subjecting the base glass to heat treatment for crystallization under a temperature within a range from 700xc2x0 C. to 780xc2x0 C. for one to seven hours.
The invention described in claim 58 is an information storage disk holding member as defined in any of claims 19, 30, 35, 36, 42 and 46 wherein the glass-ceramics are obtained by subjecting base glass obtained by melting and forming glass raw materials to heat treatment for nucleation under a temperature within a range from 650xc2x0 C. to 750xc2x0 C. for one to seven hours and further subjecting the base glass to heat treatment for crystallization under a temperature within a range from 750xc2x0 C. to 950xc2x0 C. for one to seven hours.
The invention described in claim 59 is an information storage disk holding member as defined in claim 50 wherein the glass-ceramics are obtained by subjecting base glass obtained by melting and forming glass raw materials to heat treatment for nucleation under a temperature within a range from 400xc2x0 C. to 600xc2x0 C. for one to seven hours and further subjecting the base glass to heat treatment for crystallization under a temperature within a range from 650xe2x96xa1 to 750xe2x96xa1 for one to seven hours.
The invention described in claim 60 is an information storage disk holding member made by forming a conductive film on the surface of the holding member as defined in any of claims 1, 10, 16, 19, 30, 35, 36, 42, 46 and 50.
The invention described in claim 61 is a spacer ring for an information storage disk made of the holding member as defined in any of claims 1, 10, 16, 19, 30, 35, 36, 42, 46 and 50, said holding member having a ring shape.
The invention described in claim 62 is an information storage disk drive device capable of holding one or more information storage disks on a rotor hub by means of the spacer ring as defined in claim 61.
The invention described in claim 63 is an information storage disk drive device as defined in claim 62 wherein the rotor hub and the spacer ring have a coefficient of thermal expansion which is substantially equal to that of the information storage disk.